MedImmune will chop 200 jobs and close its Mountain View and Santa Clara locations, but will beef up its Hayward site, the provider of vaccines said. The changes are part of a wrenching restructuring of the MedImmune infectious disease and vaccines research and development operations. A total of 300 jobs will be affected. However, 100 of the jobs will be shifted to existing facilities. Some of those jobs will wind in up Hayward.